According to Enoka (2002), ground reaction force (GRF) during running dont pass directly trough center of mass (CM) so it causes torque. Arm action (swing) is here to create negative momentum to stabilize trunk(?maybe I am wrong, but acc to angular momentum conservation law this is true, or I miss-readed something in this article), so without arm swing you would be rotating around (left-right) so their purpose is in lowering amplitude of this oscilations (of upper body).
My questions here are:
Is the max frequency of arm swing (during standing) somewhat conected to a max speed of run? Can this be a limiting factor in some individuals?
What about increasing/decreasing inertia (elbow angle 60-120deg)of arms and its affect on max running speed?
Is the frequency of arm swing during max. running higher/lower than doing max. arm swings during standing/sitting?
TNX
The arms CAN control the legs when things are going right but they CAN’T help when mechanics go south (pushing out the back) With good arm action the “pull” is down not back, just as the action is with the legs. A constant angle is seldom maintained with the arms usually moving from around 85 degrees in front to about 95 to 100 degrees on the back-swing, which is within the acceptable range (arms too close to the torso in front may limit hip rotation and too open in the back may change the centre of balance, delay the return, and diminish the elastic response around the shoulder). It shouldn’t take a lot of arm strength to maintain the proper arm angles or even the rate. The main contribution of upper body strength is to the general strength of the entire organism. The hand comes up to face level in front, and you pull down from there.
The arms will come towards the mid line (but not cross it) with good mechanics, as this initiates the shoulder rotation required to compensate for the counter-rotation of the hip. The mechanics must be checked on two planes- front and side to see what’s really going on.
An incomplete arm action must limit hip rotation by failing to provide sufficient counter-rotation.
The arms can be held at 90 degrees but as speed goes up the forces at work do the opening up without any conscious input. If you deliberately “break” at the elbow, you’ll loose the elastic rebound around the shoulder joint which facilitates the return, and dissipate energy from the upper arm action.
If the angle gets too small in front, it prevents full rotation at the hips by limiting compensatory rotation at the shoulder, moves the CG back slightly, forcing forward movement at the shoulders, interfering with force delivery (extension) through the hip and interfering with the natural rebound/return action of the arm at the shoulder at the completion of the back-swing, and so on and so on…
ok to answer question number 1 - I believe that it is actually the other way around, that is, that the max speed of the run is what controls the frecuency of the arm swing, as the legs are longer and heavier levers, they would be the limiting factors in cycle speed of the arms.
not really sure I understand the question, but if what you mean is… "does the acceleration and deceleration of the arms affect the run? I would say yes and no, yes because it is movement that does not help directly in pushing forward, and no, because if you consider that during the run, the legs do the same, I wouldn’t consider it a limiting factor.
Here the answer is no, when doing arm swings you are concentrating only on the arms, they are not acting as “counter weights” balancing against the rotational forces produced by the lower half of the body, where these are the limiting factors.
I ment moment of inertia (resistance of some body to angular movement change)… when you put a little weights (0.1-0.5kg) on arms, in what percent they are affecting max. speed… this is the question! Moment of inertia at shoulder can be increased by increasing elbow angle and vice versa…
SO then, what is the role of arm drills (standing, sitting) for sprint mechanics? Skill???
actually I believe the point is to have them swing freely, keeping the shoulders down, and also it could possibly be used to work all the core muscles as stabilizers as well.
“Coordinated movement of arms and legs remains the key to efficent sprinting. It is through range and force that the two coordinate. While the movement coordinates,… arms lead legs in tempo and range” (Tom Tellez)
